1. Field of the Invention
The present invention relates to a coating film peeling method and a coating film peeling apparatus for peeling a coating film from a coated resin product having the coating film on the surface of a base resin material.
2. Description of the Related Art
A recycling of resin products has been demanded in recent years for the environmental problems or for the reclamation of resources. In the field of automobile industries, for example, there has also been noted the recycling of the in-process defectives, which are made when the resin products such as bumpers or body side moldings are manufactured, or the resin products which are separated and recovered from scrapped cars.
The resin products such as bumpers are often coated on their surfaces so as to improve the appearances and qualities. In a bumper made of a resin, for example, a base material layer 101 of a resin is generally coated on its surface with a coating layer 103 through a primary layer 102, as sectionally shown at a essential portion in FIG. 14.
The base material layer 101 is made of a mixture, which is prepared by mixing a base of a thermoplastic synthetic resin or polypropylene with ethylene-propylene rubber and a filler such as talc, and is formed into a layer having a specific gravity of 0.91 to 0.98 and a thickness t of about 2 mm to 4 mm.
The primer layer 102 is made of an adhesive layer having a specific gravity of about 1.7 and a thickness of about 10 microns so as to strengthen the bonding power of the base material layer 101 and the coating layer 103. The coating layer 103 is formed by applying a paint coating which is made of a thermoset synthetic resin such as melamine or polyurethane.
When the bumper is crushed and pelletized to obtain a reclaimed material, however, the coating film chips are included in the polypropylene resin making the base material layer 101. In the molding process using the polypropylene resin material including the coating film chips, these coating film chips will obstruct the fluidicity of the molten resin to cause a defective molding in the resin product. At the same time, the coating film chips will float to the surfaces of the resin product and deteriorate the appearances of the resin product. Because of few interactions between the coating film chips and the polypropylene resin, moreover, the coating film chips will obstruct the kneading of the reclaimed resin to degrade the mechanical properties of the resin product.
When the coated resin product is to be recycled, therefore, it is essential to remove the coating films.
This coating film removing method is classified coarsely into the mechanical, physical and chemical methods. The mechanical coating film removing method is exemplified by a shot blast method and a screen mesh method. The shot blast method is for breaking and removing the coating films or deposits by blasting abrasive particles with compressed air, for example, to the coating film surface formed on the resin product. The screen mesh method is for removing the coating film chips not melted but included, by pulverizing the resin product finely and then by filtering the fine chips being heated and melted through a screen mesh.
The shot blast method removes the coating films by friction and impact and is excellent in the non-toxic properties and the environmental safety. Despite this, however, the shot blast method takes a long time for the treatment but is neither sufficient in the coating film removing efficiency nor easy for the treatment of curved portions. On the other hand, the screen mesh method is also excellent in the non-toxic properties and the environmental safety because it removes the coating film chips through the filtration. When the screen mesh is clogged, however, the extrusion pressure seriously rises to reduce the extrusion and the productivity and to have an insufficient efficiency for removing the coating film chips. The screen mesh has to be replaced so as to avoid the reduction, as caused by the clogging, in the production efficiency.
The physical coating film removing method uses a halogen solvent or various organic solvents to remove the coating films by making use of the penetration of the solvent into the interface between the coating films and the base material and the swelling phenomenon of the coating films by the solvent. Therefore, the physical coating film removing method is inferior in the environmental safety for the disposal of the waste liquid and is poorer in the coating film removing efficiency and the treating capacity but may deteriorate the base material.
Since these mechanical and physical coating film removing methods are poor in the coating film removing efficiency, the resin product using the resin material reclaimed by those methods is high in the production cost so that its application is seriously restricted.
The chemical coating film removing method is exemplified by the organic salt method for decomposing and removing the coating film chemically by cutting the ether bonds in the vicinity of the bridges of the coating film resin with an aqueous solution of ethanol containing an organic salt.
This method has a problem in the secondary treatment such as the wastewater treatment and has a poor treating capacity so that it is not preferable for the treating efficiency.
As disclosed in Japanese Patent Unexamined Publication No. 5-337941, on the other hand, there has been proposed a synthetic resin surface peeling apparatus for cutting and peeling the coating films by applying the cutting force and the frictional force to the coating films by a pair of rotary members.
In this peeling apparatus, as schematically shown in a front elevation in FIG. 12 and in a sectional view of line Ixe2x80x94I of FIG. 12 in FIG. 13, a resin product such as a body side molding 122 is transferred between rollers 123 and 124 made of a foamed synthetic resin by a pair of conveyor rollers 121. By setting the transfer velocity V of the body side molding 122 lower than the circumferential velocity of the rollers 123 and 124, high cutting and frictional forces are applied to the coating film 122a and the double adhesive tape 122b of the body side molding 122 to cut and peel the coating film 122a and the double adhesive tape 122b from the surface of the body side molding 122. By the paired conveyor rollers 121, moreover, the body side molding 122 is discharged to the outside.
In this apparatus, the resin product is brought into contact with the rotating rollers 123 and 124 made of the foamed synthetic resin. Therefore, the rollers 123 and 124 will have brittle fracture and generate dust which is unfavorable for the working environment. On the other hand, the apparatus is not suited for peeling the coating films from bent or curved resin products.
In view of the points thus far described, therefore, a first object of the invention is to provide a coating film peeling method for a coated resin product, which is excellent in the coating film removing efficiency, the environmental safety and the treating capacity to produce recycled resin products of a high quality.
Moreover, a second object of the invention is to provide a coating film peeling apparatus, which is constructed to execute the aforementioned coating film peeling method simply at a low cost.
In order to achieve the aforementioned first object, the method for peeling a coating film from a coated resin product comprises: coarsely crushing the coated resin product having a base resin material coated with the coating film; and conveying thus coarsely crushed products of the coated resin product while rubbing the same to peel the coating film from the base resin material.
According to the invention, by neither employing chemicals such as organic salts or solvents nor requiring a secondary treatment such as the wastewater treatment, the coated resin products can be coarsely crushed, and the coarsely crushed products are conveyed while being rubbed, to peel the coating films from the base resin material. With this small number of steps, it is possible to improve the coating film removing efficiency, the environmental safety and the treating capacity.
In the coating film peeling method, it is preferable that the coarsely crushed products of the coated resin products are conveyed while being mixed with an abrasive.
According to the invention, the coarsely crushed products of the coated resin product are rubbed in additional contact with the abrasive so that the separation of the coating film from the base resin material can be promoted to enhance the coating film removing efficiency to a higher level.
In order to achieve the aforementioned second object, the invention of a coating film peeling apparatus for peeling a coating film from coarsely crushed products of a coated resin product having a base resin material coated with the coating film, comprises: a cylindrical member having a loading mouth on one end side and an outlet on the other end side; a rotary member disposed rotatably within the cylindrical member and having a protrusion on its outer circumference; and a drive unit driving the rotary member rotationally, wherein the coarsely crushed products of the coated resin product are loaded into the cylindrical member from the loading mouth and then are conveyed and rubbed by a rotation of the rotary member.
According to the invention, by neither employing chemicals such as organic salts or solvents nor requiring the secondary treatment such as the wastewater treatment, the coated resin products can be coarsely crushed, and the coarsely crushed products are conveyed while being rubbed by the cylindrical member such as a cylinder and the rotary member to peel the coating films from the base resin material, thereby to improve the coating film removing efficiency, the environmental safety and the treating capacity. Moreover, the cylinder unit, the rotary member and drive unit, for example, can be constructed by utilizing the parts of the existing extrusion molding machine, for example, so that the coating film peeling apparatus can be provided simply at the low cost.
In the coating film peeling apparatus, it is preferable that the protrusion includes a helical protrusion extending helically in an axial direction of the rotary member.
According to the invention, the protrusion is the helical protrusion so that the loaded products can be reliably rubbed by one another by the turning force of the rotary member and by the extruding force of the loaded products to peel the coating film effectively from the base resin material of the coarsely crushed products.
In the coating film peeling apparatus , it is also preferable that the protrusion includes a plurality of elliptical protrusions provided in parallel in an axial direction of the rotary member, each elliptical protrusion having a substantial elliptical section as viewed in the axial direction of the rotary member, and major-axes of adjoining elliptical protrusions intersecting.
According to the invention, the protrusion includes the plurality of elliptical protrusions so that the loaded products can be rubbed while being agitated, to enhance the coating film removing efficiency to a higher level.
Further, in the coating film peeling apparatus, it is preferable that the protrusion includes: a helical protrusion extending helically in the axial direction; and a plurality of elliptical protrusions provided in parallel in an axial direction of the rotary member, each elliptical protrusion having a substantial elliptical section as viewed in the axial direction and major-axes of adjoining elliptical protrusions intersecting.
According to the invention, the loaded products can be rubbed by one another while being pressed, at the portion having the helical protrusion, and can be rubbed while being agitated under the reduced pressure at the portion having the plurality of elliptical protrusions, so that the coating film can be removed more efficiently.
In the last mentioned coating film peeling apparatus, the helical protrusion and the elliptical protrusions are combined and arranged in plurality in the axial direction.
According to the invention, the rubbing under the pressure of the loaded products and the rubbing by the agitation under the reduced pressure are repeated so that the coating film can be removed more efficiently.
In the coating film peeling apparatus the coated resin product, the pitch of the protrusion may be set to be the smaller the more downward in a conveying direction of the loaded coarsely crushed products.
In the coating film peeling apparatus, on the other hand, a diameter of the protrusion may be also set to be the larger the more downward in a conveying direction of the loaded coarsely crushed products.
According to the individual inventions, the pressure to act on the loaded products can be gradually raised to the higher level or the pressure at which the loaded products mate with each other can be prevented the more from dropping, the more downstream of their conveying direction. Therefore, the coating film peeling force by the rubbing action can always be applied to the coarsely crushed products so that the coating films can be peeled more reliably.
In the coating film peeling apparatus, it is preferable that the cylindrical member includes a first cylindrical portion and a second cylindrical portion which are formed in parallel in an axial direction of the rotary member while partially overlapping each other, and the rotary member includes a first rotary member disposed rotatably within the first cylindrical portion and a second rotary member disposed rotatably within the second cylindrical portion.
According to the invention, the peeling treatment of the coating films is performed in the first cylindrical portion and the second cylindrical portion so that the treating capacity can be enhanced to a higher level. At the same time, the loaded products migrate between the first cylindrical portion and the second cylindrical portion and are rubbed while being agitated, so that the coating films can be removed more efficiently.
The coating film peeling apparatus, further may comprise heating means for heating an inside of the cylindrical member.
According to the invention, the loaded products are heated in the cylindrical member so that the coating film peeling efficiency can be enhanced to a higher level.
In the coating film peeling apparatus, the cylindrical member may have an opening formed between the loading mouth and the outlet on the cylindrical member, the opening provided with a mesh for dropping a part of chips of the coating film peeled from the coarsely crushed products.
According to the invention, the coating film chips, as peeled off in the cylindrical member, are partially dropped to facilitate the work to separate/fractionate the base resin material and the coating films from the discharge which is excluded from the outlet of the cylindrical member.
In the coating film peeling apparatus, the cylindrical member may include a plurality of cylindrical elements removably joined to each other in an axial direction of the rotary member.
According to the invention, when the rotary member is exemplified by arranging the plurality of the portion having the helical protrusion and the portion having the plurality of elliptical protrusions in combination in the axial direction, as in the above-mentioned invention, it is possible to assemble them easily. When the cylinder is worked on its lower face, as in the above-mentioned invention, it is possible to facilitate the work.
In the coating film peeling apparatus, the cylindrical member has a roughened inner face.
According to the invention, the coating films are also peeled by the rubbing between the coarsely crushed products of the coated resin products and the inner face of the cylindrical member so that the removing efficiency and the treating capacity of the coating films can be more improved.